Remove unused model.js and its tests

Model dosen't have any reason to be present in the source code. Now
there is no difference between the dev and dist tests which are run.

Signed-off-by: Rohan Jain <crodjer@gmail.com>
Fix forever task: non-blocking server spawn

Signed-off-by: Rohan Jain <crodjer@gmail.com>
Simpler (tested) parsers instead of field classes

Field objects were not doing anything apart from the parse function,
so just defining them as a bunch of functions called parsers. Saber
exports it as `Saber.Parser` object. A parser will be
`Saber.Parser.<type>`. Also there is Saber.Parser.identity which is
used by default for unavailable parsers.

To define a new parser:

Saber.Parser.newtype = function (value, typeData) {
  // `value` will be the actual value to be parsed and
  // `typeData` can be a object which can be used to
  // configure the parser. For eg: `integer` provides
  // `radix` option to set the radix that is used with
  // parseInt function.
};

Signed-off-by: Rohan Jain <crodjer@gmail.com>